A conventional extensible rod widely applied in cleaning or agricultural tools, as shown in FIGS. 1,2, comprises an outer tube 1 and an inner tube 2 to be fitted in the outer tube 1, a tubal base 3 having an eccentric shaft 31 fitting and possible to rotate in an eccentric ring 4, a positioner 5 at the upper end of the outer tube 1, and a screw cap 6 to screw with the positioner 5.
The locking movement of the conventional extensible rod is effected by turning the eccentric ring 4 to be tightened against the eccentric shaft 31 and screwing the screw cap 6 tightly against the positioner 5.
The structure of the conventional rod has the following disadvantages.
1. The tightened relation between the eccentric shaft and the eccentric ring and the tightened relation between the eccentric ring and the inner surface of the outer tube are liable to slide off each other.
2. The locking structure of the extensible rod is rather complicated, and besides, locking or unlocking operation requires two stages, looking like double guarantees but practically not sophisticated enough.